DESCRIPTION: (applicant's abstract) Ferritin is a pivotal protein in the maintenance of intracellular iron homeostasis. Using fluorescence in situ hybridization, we have recently observed that the gene encoding the H subunit of ferritin is contained within a genetic region amplified in approximately 25% of breast cancer patients. Taken together with observed elevation in tissue ferritin in breast cancer, this suggests that increases in ferritin play a consistent and important role in the biology of this diseases. The goal of this proposal is to define that role. We will test the hypothesis that ferritin H amplification alters intracellular iron balance in breast cancer cells and facilitates breast cancer growth. The aims of this proposal are: 1) to quantify the relationship between amplification of the ferritin H gene and levels and composition of ferritin H mRNA and protein, 2) to understand whether intracellular iron status differs in breast cells with and without a ferritin amplification, 3) to explore whether ferritin H amplification impacts breast cancer cell growth, and 4) to understand structural features of the amplicon containing ferritin H, particularly the linkage of ferritin amplification to the amplification of adjacent genes. The experiments described in this proposal will use both breast cancer cell lines and primary tumor tissue to approach the question of whether ferritin H amplification alters the iron balance of breast cancer cells, and whether it affects tumor cell growth. By defining at a molecular level the effects of ferritin amplification on the biological behavior of breast cancer cells, we will enhance understanding of the fundamental question of how iron handling differs in tumor and non-tumor cells. Ultimately, this may suggest whether therapies which target iron metabolism deserve consideration in selected breast cancer patients.